Alnus rohlenae Vít, Douda & Mandák

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Credits

Tim Baxter & Hugh A. McAllister (2024)

Recommended citation
Baxter, T. & McAllister, H.A. (2024), 'Alnus rohlenae' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/alnus/alnus-rohlenae/). Accessed 2024-04-12.

Genus

  • Alnus
  • Subgen. Alnus, Sect. Glutinosae

Glossary

adaxial
(especially of surface of a leaf) Upper; facing towards the axis. (Cf. abaxial.)
autopolyploid
State of increased ploidy resulting from doubling of the normal two sets of chromosomes in a single species.
domatia
Cavity or tuft of hairs that acts as a shelter for insects or other creatures.
emarginate
Notched at the apex.
glabrous
Lacking hairs smooth. glabrescent Becoming hairless.
subspecies
(subsp.) Taxonomic rank for a group of organisms showing the principal characters of a species but with significant definable morphological differentiation. A subspecies occurs in populations that can occupy a distinct geographical range or habitat.

Credits

Tim Baxter & Hugh A. McAllister (2024)

Recommended citation
Baxter, T. & McAllister, H.A. (2024), 'Alnus rohlenae' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/alnus/alnus-rohlenae/). Accessed 2024-04-12.

Tree to 35 m. Bark grey to grey-brown, becoming fissured with age. Twigs brown to silvery grey, thin, viscid, pubescent when young. Buds 5–6 mm, obovate, apex rounded, villous, scales 2–3, brown, viscid, stipitate, stipe 4–6 mm. Leaves obovate to suborbicular, 5–9 × 4–8 cm, apex broadly acute to emarginate, base cuneate, margin lobulate with teeth dentate, craspedodromous, 7–10 pairs of lateral veins, blade adaxially ± glabrous, abaxially glabrous to pubescent, always pubescent along veins and with hairy domatia of different colour to veins, light green above and below. Petiole 8–28 × 1–2 mm, glabrous. Staminate catkins in terminal cluster, suberect in bud, pendulous at anthesis, 20–60 × 2–6 mm at anthesis. Pistillate catkins 2–4 in pendent racemose cluster below males, 2 × 1 mm, peduncle 4–20 mm. Fruit ovate-elliptic, 11–21 × 7–15 mm, scales woody, apices rounded with 4 divergent lobes, dark brown to black at maturity, peduncle 35 mm, branchlets 4–13 mm. Seeds wingless, 2 × 2 mm, mid-brown. Flowering February to April. Tetraploid, 2n=56. (Vit et al. 2017).

Distribution  AlbaniaGreeceMontenegroSerbia

Habitat Stream and riverine forests in mountain valleys and hardwood forests dominated by Fraxinus angustifolia and Platanus orientalis. Associated with frequently flooded alluvia close to the active channels of streams and rivers.

USDA Hardiness Zone 3-7

RHS Hardiness Rating H7

Conservation status Not evaluated (NE)

Alnus rohlenae is a recently described tetraploid species (Vit et al. 2017) from south-eastern Europe, in the western part of the Balkan Peninsula, covering the northern part of Greece, Albania, Montenegro, Serbia and possibly adjacent regions. It is an autopolyploid of A. glutinosa, most likely derived during a period of isolation, probably during glaciation, from refugia in this region. Of note are triploid A. glutinosa and probable hybrids that occur in the same region as diploid A. glutinosa. These populations still retain the emarginate apices typical of the species, but much less so than further north and west, and appear somewhere nearer subspecies barbata. It is allied to A. lusitanica, another tetraploid species also described in the same paper. In overall appearance A. rohlenae is similar to A. glutinosa but smaller in all parts, especially cones. It is distinguished by the hairy domatia (hair floccules) of different colour than the hairs along the lateral veins. The adaxial leaf surface (as well as annual shoots and buds) are markedly hairy, in contrast to the glabrous A. glutinosa.

Alnus rohlenae is rare in cultivation. Plants were introduced by the Belgian Alnus Seed Bank from the Sperchios River valley above Lamia, central Greece. Mature trees can be found in the UK at Ness and Hilliers where they have grown into somewhat unassuming but drought tolerant forms of A. glutinosa.